/*
 * @Description: 地图经纬度算法相关
 * @Date: 2022-04-02 17:40:33
 * @Author: yeming
 */

/**
  * 根据一个经纬度及距离角度，算出另外一个经纬度
  * @param {Number} lng 经度 113.3960698
  * @param {Number} lat 纬度 22.941386
  * @param {Number} azimuth 方位角(角度) 45 ---- 正北方：000°或360° 正东方：090° 正南方：180° 正西方：270°
  * @param {Number} distance 90000距离(米)
  *
  * 1、角度转换为弧度公式：弧度=角度×(π ÷度180 )
  * 2、弧度转换为角度公式： 角度=弧度×（180÷π）
*/
export function getLonlatByDistancsAndAzimuth (lng, lat, azimuth, distance) {
  // 大地坐标系资料WGS-84 长半径a=6378137 短半径b=6356752.3142 扁率f=1/298.2572236
  var a = 6378137;
  var b = 6356752.3142;
  var f = 1 / 298.257223563;

  var lon1 = lng * 1;
  var lat1 = lat * 1;
  var s = distance;
  var alpha1 = azimuth * (Math.PI / 180) // mapNumberUtil.rad(azimuth);
  var sinAlpha1 = Math.sin(alpha1);
  var cosAlpha1 = Math.cos(alpha1);

  // var tanU1 = (1 - f) * Math.tan(mapNumberUtil.rad(lat1));
  var tanU1 = (1 - f) * Math.tan(lat1 * (Math.PI / 180));
  var cosU1 = 1 / Math.sqrt((1 + tanU1 * tanU1)), sinU1 = tanU1 * cosU1;
  var sigma1 = Math.atan2(tanU1, cosAlpha1);
  var sinAlpha = cosU1 * sinAlpha1;
  var cosSqAlpha = 1 - sinAlpha * sinAlpha;
  var uSq = cosSqAlpha * (a * a - b * b) / (b * b);
  var A = 1 + uSq / 16384 * (4096 + uSq * (-768 + uSq * (320 - 175 * uSq)));
  var B = uSq / 1024 * (256 + uSq * (-128 + uSq * (74 - 47 * uSq)));

  var sigma = s / (b * A), sigmaP = 2 * Math.PI;
  while (Math.abs(sigma - sigmaP) > 1e-12) {
    var cos2SigmaM = Math.cos(2 * sigma1 + sigma);
    var sinSigma = Math.sin(sigma);
    var cosSigma = Math.cos(sigma);
    var deltaSigma = B * sinSigma * (cos2SigmaM + B / 4 * (cosSigma * (-1 + 2 * cos2SigmaM * cos2SigmaM) -
      B / 6 * cos2SigmaM * (-3 + 4 * sinSigma * sinSigma) * (-3 + 4 * cos2SigmaM * cos2SigmaM)));
    sigmaP = sigma;
    sigma = s / (b * A) + deltaSigma;
  }

  var tmp = sinU1 * sinSigma - cosU1 * cosSigma * cosAlpha1;
  var lat2 = Math.atan2(sinU1 * cosSigma + cosU1 * sinSigma * cosAlpha1,
    (1 - f) * Math.sqrt(sinAlpha * sinAlpha + tmp * tmp));
  var lambda = Math.atan2(sinSigma * sinAlpha1, cosU1 * cosSigma - sinU1 * sinSigma * cosAlpha1);
  var C = f / 16 * cosSqAlpha * (4 + f * (4 - 3 * cosSqAlpha));
  var L = lambda - (1 - C) * f * sinAlpha *
    (sigma + C * sinSigma * (cos2SigmaM + C * cosSigma * (-1 + 2 * cos2SigmaM * cos2SigmaM)));

  var revAz = Math.atan2(sinAlpha, -tmp); // final bearing

  var lngLatObj = { lng: lon1 + L * (180 / Math.PI), lat: lat2 * (180 / Math.PI) }
  return lngLatObj;
}

